1. Field of the Invention
This invention relates generally to circuit breakers and, more particularly, to circuit breakers of the electromagnetic type including an operating mechanism and an operating handle.
2. Background Information
Circuit breakers of the electromagnetic type are shown, for example, in U.S. Pat. Nos. 3,329,913; and 4,151,386.
Such electromagnetic circuit breakers typically comprise an operating mechanism including a movable contact, which is mounted on a movable arm, and a fixed or stationary contact. An operating handle is coupled to the movable arm via a linkage mechanism, part of which comprises a collapsible toggle assembly. The movable and stationary contacts are operated between contacts xe2x80x9copenxe2x80x9d and contacts xe2x80x9cclosedxe2x80x9d positions by pivoting the operating handle. The circuit breaker further comprises an electromagnetic device which, in response to one or more predetermined electrical conditions, collapses the toggle assembly to a broken state, in order to electrically trip xe2x80x9copenxe2x80x9d the separable movable and stationary contacts.
During on and off operation, the operating mechanism employs a rigid linkage mechanism, including first and second links, to the operating handle. The first end of the second link is pivotally mounted to the second end of the first link and the second end of the second link is pivotally mounted to the movable arm. This provides an early (i.e., relative to handle throw) toggle-on point. At the point where the operating mechanism toggles and the unbroken linkage mechanism begins to move, there is very little energy stored in the operating mechanism springs. As a result, the circuit breaker can be xe2x80x9cteasedxe2x80x9d on, which causes undesirable and potentially damaging arcing to the separable contacts.
xe2x80x9cSlow makexe2x80x9d is defined as the closing velocity of the circuit breaker separable contacts being directly dependent upon the closing speed of the operating handle. For a circuit breaker operating at relatively high voltages (e.g., 480 to 600 VAC), this results in a greater tendency for the separable contacts to weld closed, and significantly reduces the number of switching operations in the operating life of the circuit breaker.
U.S. patent application Ser. No. 10/185,858, filed Jun. 27, 2002, discloses a circuit breaker including a pivot lever having a first arm with a first end adapted for engagement with a movable contact arm, and a second arm having a second end adapted for engagement with an operating handle assembly. The first end of the pivot lever carries a U-shaped hook member pivotally disposed thereon. The hook member has a J-shaped hook, which is adapted for engagement with the movable contact arm, and a J-shaped pivot end, which is pivotally mounted in an opening of the first arm. In order to eliminate the dependency between the movable contact arm and the operating handle assembly, the J-shaped hook initially hooks the movable contact arm. The pivot end of the hook member is inserted into the first or free end of the pivot lever. The pivot lever pivots about a pin and translates the hook member and the movable contact arm movement up to the operating handle assembly. The second or handle end of the pivot lever interacts with a blocking disk of the operating handle assembly, which disk rotates about the same center as the operating handle, but is allowed independent movement.
There is room for improvement in circuit breakers.
These needs and others are met by the present invention, which provides a flexible cantilever lever for a circuit breaker operating mechanism. The flexible cantilever lever delays the motion of an independent operating handle link and the operating mechanism linkage until after a toggle-point is reached. For example, this allows relatively more energy to be stored in operating handle extension springs at the time the link and linkage begin to move. As a result, it is not possible to xe2x80x9cteasexe2x80x9d the circuit breaker closed. The flexible cantilever lever holds the link and linkage in the open position of the operating mechanism and releases the link and linkage as the circuit breaker operating handle moves from the open position toward the closed position of the operating mechanism, in order to snap close the separable contacts.
For example, the flexible cantilever lever may be fixed within the circuit breaker case. With the circuit breaker in the open position, the flexible cantilever lever may rest against a projection of the independent handle link in the direction of travel with minimal engagement. The flexible cantilever lever latches this link and the linkage in place and stops motion of the linkage until sufficient mechanism spring force is achieved.
As one aspect of the invention, a circuit breaker comprises: a case; separable contacts; an operating mechanism for opening and closing the separable contacts, the operating mechanism including an open position, a snap closed position, a closed position, an operating handle for moving the operating mechanism between the open and closed positions, a movable contact arm carrying one of the separable contacts, a link having a first end pivotally mounted with respect to the case, a second end and a projection, and a linkage having a first end and a second end, the first end of the linkage being pivotally mounted to the second end of the link, the second end of the linkage being pivotally mounted to the movable contact arm; and a flexible cantilever lever fixed within the case, engaging the projection of the link and holding the link in the open position of the operating mechanism, the flexible cantilever lever flexing and releasing the projection of the link and releasing the link as the operating handle moves the operating mechanism from the open position to the snap closed position.
The operating mechanism may further include a pivot and at least one extension spring for moving the operating mechanism to close the separable contacts. The operating handle may include a first portion extending through an opening of the case and a second portion within the case, the at least one extension spring extending between the second portion and the pivot. The flexible cantilever lever may delay motion of the link and the linkage, with the at least one extension spring being extended as the operating handle moves from the open position to the snap closed position of the operating mechanism, in order to load the linkage until the flexible cantilever lever flexes and releases the projection of the link, with the load being released as a snap close action, in order that the at least one extension spring drives the linkage and drives the movable contact arm carrying a movable contact toward a fixed contact.
The flexible cantilever lever may have an inverted T-shape, with a base portion fixed to the case and a cantilever portion extending within the case. The cantilever portion may have a first side and a second side, with the first side engaging the projection of the link and holding the link in the open position of the operating mechanism. As the operating handle moves the operating mechanism from the closed position toward the open position, the second side of the cantilever portion may engage the projection of the link. As the operating handle moves further from the closed position toward the open position, the cantilever portion may flex and release the projection of the link.
As another aspect of the invention, a circuit breaker comprises: a case; separable contacts; an operating mechanism for opening and closing the separable contacts, the operating mechanism including an open position, a closed position, an operating handle for moving the operating mechanism between the open and closed positions, a movable contact arm carrying one of the separable contacts, a link having a first end pivotally mounted with respect to the case, a second end and a projection, and a linkage having a first end and a second end, the first end of the linkage being pivotally mounted to the second end of the link, the second end of the linkage being pivotally mounted to the movable contact arm; and a flexible cantilever lever fixed within the case, engaging the projection of the link and holding the link in the open position of the operating mechanism, the flexible cantilever lever flexing and releasing the projection of the link as the operating handle moves the operating mechanism from the open position toward the closed position.
As another aspect of the invention, a circuit breaker comprises: a case; separable contacts; an operating mechanism for opening and closing the separable contacts, the operating mechanism including an open position, a snap closed position, a closed position, an operating handle for moving the operating mechanism between the open and closed positions, a movable contact arm carrying one of the separable contacts, and a linkage between the operating handle and the movable contact arm; and a flexible cantilever lever fixed within the case, engaging the projection of the linkage and holding the operating mechanism in the open position, the flexible cantilever lever flexing and releasing the projection as the operating handle moves the operating mechanism from the open position to the snap closed position.